Chess Elo Calculator
Enter your rating and your tournament games, and watch your new FIDE or national Elo update live.
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Elo flow
Every time you fill in an opponent's rating, a new row is added automatically.
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What the Elo rating is and how it works
Elo is the rating system that measures the relative strength of chess players. It was created by the physicist Arpad Elo and officially adopted by FIDE in 1970; today it is used by every federation in the world, from FIDE down to national and regional federations.
The idea is simple: the points you gain depend on how surprising the result is. Beating a much weaker opponent earns you almost nothing; beating a much stronger one earns you a lot. Losing works the same way in reverse. Over time, your rating converges on your real playing strength.
How the Elo change is calculated
For each game, the expected score is calculated from the rating difference between you and your opponent, using FIDE's official conversion table (very close to the formula E = 1 / (1 + 10^((opponent's Elo − your Elo) / 400))). Against an opponent with your exact rating the expectation is 0.5 points; against one rated 200 points lower, 0.76.
The change for each game is K × (result − expected), where the result is 1 for a win, 0.5 for a draw and 0 for a loss. The rating difference is capped at ±400 points (FIDE's "400-point rule").
In a tournament, every game is calculated against your initial rating — your Elo is not updated round by round. The final change is the sum of the per-game changes, which is exactly what this calculator does.
Which K-factor applies to me?
New players (until they complete 30 rated games) and players under 18 rated below 2300.
Everyone else rated below 2400. This is the most common K.
Players who have ever reached 2400 Elo. K stays at 10 even if they later drop below 2400.
These are FIDE's values for standard games. Most national and regional federations use the same formula and the same K tiers: pick whichever matches your category (new/under-18, standard, or elite).
A step-by-step example
Say you are rated 1947 with K=20 and you play a three-round tournament: you beat an opponent rated 1673, draw with one rated 1761 and lose to one rated 1621.
The expected scores are 0.83, 0.74 and 0.87 points (total: 2.44). You scored 1.5. The change is 20 × (1.5 − 2.44) = −18.8 points: your new Elo would be 1928. Try it in the calculator and you will see the game-by-game breakdown.
FIDE Elo and national Elo: why do I have two ratings?
FIDE maintains the international rating list, but most national and regional federations keep their own Elo list, updated by the same tournaments under their own regulations. That is why the same tournament can change each of your ratings differently: your opponents hold different ratings on each list, and the K-factor may differ too.
This calculator works for both lists: run the numbers with the rating and K-factor of whichever list you want, then swap the values for the other — the result updates instantly. Soon you will be able to load both lists at once from a tournament results link.
Frequently asked questions
How is the Elo change after a tournament calculated?
For each game the expected score is derived from the rating difference (FIDE's official conversion table, approximately E = 1/(1+10^((Rb−Ra)/400))) and the change is K × (result − expected). The tournament change is the sum over all games, always calculated from your initial rating.
Which K-factor should I use?
Under FIDE rules: K=40 if you are new or under 18 (rated below 2300), K=20 up to 2400, and K=10 if you have ever reached 2400. Most national federations use the same tiers: pick whichever applies to you.
Does it work for national or regional ratings?
Yes. Virtually every federation uses the standard Elo formula and the same K-factor tiers as FIDE. Pick whichever applies to you and the calculation is valid for any list.
What if an opponent has no rating?
Leave the box empty: that game does not count for that list. This is the same criterion federations apply when an opponent is unrated on the corresponding list.
What is a tournament performance rating?
It is the level you played at in that specific tournament: the average rating of your opponents plus an adjustment (FIDE's dp table) based on your score percentage. Scoring 50% means performing exactly at your opponents' average.
Why does my Elo gain less than my opponent loses?
Because each player has their own K-factor. If you have K=20 and your opponent K=40, the same game moves twice as many points for them as for you. The system is not exactly zero-sum.
More tools from EloCheck
Look up any rated player in Spain, follow their Elo history and games, or compare up to six players at once.